Vanadium In Water Samples Research Articles

Multi-Walled Carbon Nanotubes Magnetic Composite as an Adsorbent for Preconcentration and Determination of Trace Level Vanadium in Water Samples

Magnetic solid phase microextraction (m-SPME) is a well-defined strategy for the preconcentration and separation of hydrophobic species from aqueous samples without the use of toxic organic solvents. This work identifies a new analytical procedure for trace level vanadium(V) by inductively coupled plasma mass spectrometry coupled to magnetic solid phase microextraction. The procedure is based on the preconcentration of the V(V)–H2O2–4-(2-pyridylazo)resorcinol complex. Magnetic Fe3O4 nanoparticles decorated multi-walled carbon nanotubes as an adsorbent were investigated systematically. The calibration curve obtained by using m-SPME for vanadium(V) was linear from 0.011 to 10 µg/L. The method detection limit was found to be 1.5 ng/L. The m-SPME method was applied to the assay of vanadium in a certified reference water sample and the result was in total balance with the declared value. Finally, the proposed method was applied to the determination of vanadium in real water samples.

Application of Electrochemical Sensor Based on Lead Film Electrode in Trace Vanadium (V) Determination by Adsorptive Stripping Voltammetry

A simple and fast method for the determination of vanadium in water samples was established using adsorptive stripping voltammetry. The proposed method includes the formation of a complex by reacting vanadium with cupferron and its adsorption on the in situ plated lead film electrode used as a working electrode. The optimum analytical conditions include supporting electrolyte containing 0.3-mol L−1 acetate buffer pH = 5.6, ${3} \times {10}^{-4}$ mol L−1 Pb(II) and ${7} \times {10}^{-{4}}$ mol L−1 cupferron. A linear response of V(V) in the concentration range of ${1} \times {10}^{-9}$ to ${7} \times {10}^{-8}$ mol L−1 (r = 0.998) was obtained with the detection limit of ${3.2} \times {10}^{-10}$ mol L−1 using accumulation time of 30 s. Selectivity of the method was determined by investigating the influence of a number of foreign ions. The interferences of surfactants were precisely studied and successfully minimized by preliminary mixing with resin. The accuracy of the method was tested by analyzing certified reference material (SPS-WW1 waste water) and river water.

Determination of vanadium in water samples from Brazilian mineral spring (Ibirá Spa) using ICP-MS

A methodology was developed for the determination of vanadium in water samples from a hydromineral spa located in Ibirá, Sao Paulo State, Brazil and in bottled drinking water, employing inductively coupled plasma mass spectrometry (ICP-MS). Evaluation of matrix isobaric interferences focused on the 35Cl16O+ polyatomic species at m/z 51. The determinations were carried out in standard and kinetic energy discrimination (KED) modes. Optimization of the helium flow rate in the KED mode showed that the most effective interference correction was achieved at a flow rate of 5.0mLmin−1. The limits of detection (LOD) were 0.0097 and 0.0094μgL−1 for the standard and KED modes, respectively. The concentrations of vanadium quantified in the samples studied ranged from 65.2±0.36 to 831±8.7μgL−1. The accuracy of the method was confirmed by analysis of a certified reference material for water (NIST 1640A), achieving a recovery of 101%.

Simultaneous Spectrophotometric Determination of Iron (III) and Vanadium (V) in Water Samples Using a Combination of Partial Least Squares Regression and Solid Phase Extraction with Modified Octadecyl Silica Membrane Disks

In this work solid phase extraction had been implemented with fiber optic-linear array detection spectrometry and partial least squares (PLS) multivariate calibration approach for simultaneous determination of ultra trace amounts of metals with complexes which have overlapping spectra. An octadecyl silica membrane disk modified with N-benzoyl-Nphenylhydroxylamine (BPHA) in combination with partial least squares regression (PLS) was used for simultaneous preconcentration and spectrophotometric determination of iron and vanadium in water samples. The method was based on the retention of V(V) and Fe(III) on the disks modified by BPHA in the pH range of 2.0-4.5. The retained ions were eluted with 3 mL of methyl isobutyl ketone and were measured spectrophotometrically. The data obtained from the experiments were processed by partial least squares chemometric method. PLS was applied for multivariate calibration and noise reduction through eliminating of the less important latent variables. Under the optimum conditions, for preconcentrating the analytes from 100 mL sample, the linear dynamic ranges were 14–320 µg L-1 and 10–530 µg L-1 and the detection limits were 4.2 µg L-1 and 2.5 µg L-1 for V(V) and Fe(III), respectively. The method was successfully applied to the determination of analytes in several categories of water samples. The accuracy was assessed through the recovery experiments, independent analysis by graphite furnace atomic absorption spectrometry and the analysis of a certified reference water sample. Keywords: Solid phase extraction, chemometrics, spectrophotometry, iron (III) and vanadium (V) determination.

Automatic integrated system for catalytic spectrophotometric determination of vanadium in water samples

Automatic microfluidic system for catalytic spectrophotometric determination of vanadium.

A simple flow-injection chemiluminescence method for the determination of trace pentavalent vanadium in water samples

A simple method for rapid determination of trace pentavalent vanadium in natural water was presented by flow-injection chemiluminescence (CL). Through water injection, luminol and potassium permanganate were eluted from the anion exchange column to generate the CL, which was enhanced in the presence of V(V). Under the optimum conditions, the increased CL intensity was linear with V(V) concentration in the range from 0.1 to 100 ng mL−1. The limit of detection was 50 pg mL−1 (3σ) and the relative standard deviation (RSD) was 2.24% (n = 5) for a 1.0 ng mL−1 V(V). At a flow rate of 2.0 mL min−1, one cycle of analysis could be performed in 0.5 min with a RSD of less than 3.0%. The proposed method was successfully applied to the determination of vanadium in natural water.

Catalytic-adsorptive determination of vanadium in solutions of 2,3-dihydroxybenzaldehide and bromate-ions

The influence of bromate-ions on polarographic behavior of the complex of vanadium with 2,3-dihydroxybenzaldehide in acetate buffer solutions with pH 4.7–5.5 has been examined. Using alternating-current polarography, chronovoltammetry with linear sweep of potential, square-wave voltammetry it has been demonstrated, that the electrode process is complicated by adsorption of ligand and formed complexes of vanadium with ligand. In the presence of bromate-ions the analytical signal increases more than one order. A sensitive catalytic-adsorptive method has been developed for determination of vanadium. The vanadium complex accumulation has been carried out at the potential −0.2 V (saturated calomel electrode (SCE) – a reference electrode) in a solution with pH 5.4 in the presence of 5 × 10 −5 М 2,3-dihydroxybenzaldehide and 0.1 М KBrO 3. The detection limit for the accumulation time of 30 s is 2 × 10 −10 М and the reduction current of vanadium complex is linear from 5 × 10 −8 M to 5 × 10 −10 М (the calibration graph is y = 1.5533 x + 39.371 with correlation coefficient of 0.9998). The proposed method has been successfully applied to determination of vanadium in water samples of the Prut River (Republic of Moldova).

Solidified floating organic drop microextraction and spectrophotometric determination of vanadium in water samples

Solidified floating organic drop microextraction (SFODME) was used as a sample preparation method prior to spectrophotometric determination of trace amounts of vanadium in water samples. 8-Hydroxyquinoline (oxine) was used as the chelating agent. The main parameters affecting the performance of SFODME, such as pH, concentration of oxine, extraction time, sample and organic phase volume, extraction temperature, and the nature of the organic solvent, were optimized. Under the optimized conditions, an enhancement factor of 38, detection limit of 0.97 \mu g L^{-1}, and good relative standard deviation of \pm 3.9% at 10 \mu g L^{-1} were obtained. The method was successfully applied to the determination of vanadium in tap water, well water, river water, and sea water. The accuracy of the method was assessed through a recovery experiment and independent analysis by graphite furnace atomic absorption spectrometry.

A sensitive method for determining total vanadium in water samples using colorimetric-solid-phase extraction-fiber optic reflectance spectroscopy

A selective colorimetric-solid-phase extraction (C-SPE) method for the determination of total vanadium in water samples was developed. This method introduced a new variation of C-SPE. The colour reaction is based on the reaction of vanadium(V) ternary complex formed with 1-(2-Pyridylazo)-2-naphtol (PAN) in the presence hydrogen peroxide (H 2O 2). In this technique, the target analytes in samples are extracted onto solid matrix loaded with a colorimetric reagent and then quantified directly on the adsorbent surface by using a miniature fiber optic reflectance spectrometer. The measurements were carried out at a wavelength of 589.4 nm since it yielded the largest divergence different in reflectance spectra before and after reaction with the vanadium. The overall time required for the C-SPE procedure was ∼20 min. The amount of concentrated V is then determined in a few seconds by using miniature reflectance spectrometer. At the optimal conditions, a calibration curve was constructed, revealing a linear range of 0.05–0.52 mg L −1 and a detection limit as low as 0.01 mg L −1 while the RSD lower than 2.8%. In order to verify the accuracy of the method, a certified reference water samples (TMDA) were analysed and the results obtained were in good agreement with the certified values. The proposed method was applied to the determination of vanadium in tap water, seawater samples with a recovery for the spiked samples in the range of 98–102%.

Trace determination of vanadium(V) using anodic adsorptive voltammetry at a glassy carbon electrode modified with multi-walled carbon nanotubes

A glassy carbon electrode modified with multi-walled carbon nanotubes (MWCNT) was prepared and the determination of trace amount of vanadium(V) based on the anodic adsorptive voltammetry of the vanadium-alizarin red S (ARS) complex is described for the first time. The results show that the sensitivity and the selectivity of the method are excellent. The second derivative linear scan voltammograms of the complex were recorded using a polarographic analyzer in the range from 0 to 1,000 mV (vs. SCE). It was found that the complex can be adsorbed on the surface of the electrode, yielding a peak at about 706 mV, corresponding to the oxidation of ARS in the complex. The peak current increases linearly with the V(V) concentration in the range of 6.0 nM to ∼1.0 μM (4.0 μM ARS), 2.0 μM∼10 μM (40 μM ARS) and the detection limit (at S/N = 3) was 2.0 nM (accumulation time 120 s). The method was successfully applied to the determination of trace amounts of vanadium in water samples.

Determination of Trace Vanadium by Adsorptive Stripping Voltammetry at a Carbon Paste Electrode

AbstractA method for the voltammetric determination of vanadium using a carbon paste electrode (CPE) was described. The new procedure is based on the adsorptive accumulation of the V(V)‐alizarin red S(ARS) complex onto the surface of the CPE, followed by the electrochemical reduction of adsorbed species. The optimal experimental conditions include the use of 0.10 mol/L acetate buffer (pH 5.1), 1.0×10−5 mol/L ARS, an accumulation potential of −0.10 V (versus SCE), an accumulation time of 2 min, a scan rate of 200 mV/s and a second‐order derivative linear scan mode. The reduction peak for the complex appears at −0.52 V. The peak current is proportional to the concentration of V(V) over the range of 0.10–15.0 μg/L, and the detection limit is 0.04 μg/L for a 2 min adsorption time. The relative standard deviations(n=8) for 2.0 and 0.50 μg/L V(V) are 3.1 and 4.7%, respectively. The proposed method was applied to the determination of vanadium in water samples.

Selective determination of total vanadium in water samples by cloud point extraction of its ternary complex

A highly sensitive micelle-mediated extraction methodology for the preconcentration of trace levels of vanadium as a prior step to its determination by flame atomic absorption spectrometry (FAAS) has been developed. Vanadium was complexed with 1-(2-pyridylazo)-2-naphthol (PAN) and hydrogen peroxide in acidic medium (0.2 mol L −1 phosphoric acid) using Triton X-100 as surfactant and quantitatively extracted into a small volume of the surfactant-rich phase after centrifugation. The color reaction of vanadium ions with hydrogen peroxide and PAN in phosphoric acid medium is highly selective. The chemical variables affecting cloud point extraction (CPE) were evaluated and optimized. The R.S.D. for 5 replicate determinations at the 20 μg L −1 V level was 3.6%. The calibration graph using the preconcentration system for vanadium was linear with a correlation coefficient of 0.99 at levels near the detection limits up to at least 0.6 μg L −1. The method has good sensitivity and selectivity and was applied to the determination of trace amounts of vanadium in water samples with satisfactory result. The proposed method is a rare application of CPE-atomic spectrometry to vanadium assay, and is superior to most other similar methods, because its useful pH range is in the moderately acidic range achieved with phosphoric acid. At this pH, many potential interferents are not chelated with PAN, and iron(III) as the major interferent is bound in a stable phosphate complex.

Flow-injection spectrophotometry of vanadium by catalysis of the bromate oxidation of N, N′-bis(2-hydroxyl-3-sulfopropyl)-tolidine

A highly sensitive flow-injection method is proposed for the catalytic determination of vanadium(V) at sub-nanogram per milliliter levels using a new indicator reaction. The method is based on the catalytic effect of vanadium(V) on the bromate oxidation of N, N′-bis(2-hydroxyl-3-sulfopropyl)-tolidine. 1,2-Dihydroxybenzene-3,5-disulfonate was used as an activator in the vanadium(V)-catalyzed reaction and significantly enhanced the sensitivity of the method. Vanadium(V) in the range 0.01–3.0 ng ml −1 was easily determined with sampling rate of about 30 h −1. Vanadium(IV) could be also determined. The limit of detection (S/N=3) was 0.008 ng ml −1 and the relative standard deviations were 1.4 and 1.6% for ten determinations of 0.2 ng ml −1 vanadium(IV) and vanadium(V), respectively. Interferences from metal ions could be suppressed by the addition of ethylenediamine- N, N, N′, N′-tetrakis(methylenephosphonic acid) as a masking agent. The proposed method was successfully applied to the determination of vanadium in water samples.

Determination of vanadium in water samples by reaction cell inductively coupled plasma quadrupole mass spectrometry

An inductively coupled plasma quadrupole mass spectrometer (ICP-QMS) equipped with a dynamic reaction cell (DRC) was used for the determination of vanadium and its species in water samples. The effect of the operating conditions of the DRC system was studied in order to obtain the best signal to noise ratios. The potentially interfering 35Cl16O+ and 34S16OH+ at the vanadium m/z value of 51 were reduced in intensity by approximately four orders of magnitude by using NH3 as the reaction cell gas in the DRC. The detection limit for 51V was 0.006 ng ml−1. In addition, reversed-phase ion-pair liquid chromatography (LC) was coupled with ICP-MS for the determination of various vanadium species. The limits of detection for VIV and VV were 0.007 and 0.013 ng ml−1 V at m/z 51, respectively, based on peak height. This method was applied to the determination of vanadium in NRCC SLRS-3 Riverine Water reference sample, NRCC SLEW-2 Estuarine Water reference sample and water samples collected locally. The result for the reference sample SLRS-3 agreed satisfactorily with the reference value. The results for which no reference values were available were also found to have satisfactory recoveries. The recovery was in the range of 87–109% and the precision between sample replicates was better than 14% for all the determinations.

Determination of trace vanadium in various waters by differential pulse adsorptive stripping voltammetry

AbstractA sensitive voltammetric method is developed for the determination of trace amounts of vanadium in various water samples. The method is based on the preconcentration of the VV‐2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol (5‐Br‐PADAP) complex at a potential of −0.5 V (vs. Ag/AgCl). The adsorbed complex is then reduced, producing a response with a peak potential of −0.8 V. The catalytic action of bromate ions on the reduction of the VV‐5‐Br‐PADAP complex has also been investigated. The high catalytic currents obtained in presence of bromate ions are taken advantage of enhancing the sensitivity of the method. From the preliminary studies the optimal conditions for the determination of vanadium by differential pulse adsorptive stripping voltammetry have been established. The interference of various elements in this method has also been studied. The method of standard addition is employed in evaluating the concentration of vanadium in water samples. The determination limit is 20 ng/L and the RSD is 12% for vanadium concentrations of 500 ng/L.

Determination of titanium and vanadium in water samples by inductively coupled plasma mass spectrometry with on-line preconcentration

A matrix–analyte separation and preconcentration technique was developed for inductively coupled plasma mass spectrometry (ICP-MS). A miniature chelated ion-exchanger column of SO3-CM quinolin-8-ol–cellulose (Knapp Logistic Automation, Graz, Austria) was used to increase the sensitivity for multielement measurements by ICP-MS. The technique was used to preconcentrate Ti and V from natural water. The detection limits obtained were 0.02, 0.01 and 0.001 ng ml–1 for 47Ti, 48Ti and 51V, respectively.

Reversed-phase high-performance liquid chromatographic separation and determination of titanium, vanadium, niobium and tantalum ternary complexes with hydrogen peroxide and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol

The simultaneous separation of ternary complexes of TiIV, NbV and TaV with hydrogen peroxide and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) was evaluated using reversed-phase high-performance liquid chromatography with a C18 column. Moreover, simultaneous separation of a VV—H2O2—5-Br-PADAP ternary complex and a VV– 5-Br-PADAP binary complex was carried out using the C18 column. The chelates were detected at 590 nm and the calibration graphs (20 µl of sample was injected) were linear for 0.015–0.4 µg ml–1 of TiIV, 0.001–0.08 µg ml–1 of VV, 0.004–0.1 µg ml–1 of NbV and 0.01–0.3 µg ml–1 of TaV. When the S/N ratio is 3, the detection limits for V, Nb, Ta and Ti were 0.15, 0.5, 2.0 and 2.5 ppb, respectively. The method was applied to the direct determination of vanadium in water samples and the simultaneous determination of titanium, niobium and tantalum in human hair.

Microdetermination of vanadium in water samples.

The proposed method incorporates preconcentration of vanadium in water samples by its coprecipitation on ferric hydroxide at pH 8.0-9.6 which is redissolved in sulphuric acid; this is followed by extraction with N-phenylbenzohydroxamic acid (PBHA). The precision and accuracy of the newly developed method was ascertained by analysing EPA (Environmental Protection Agency, U.S.A.) standard water samples.